Since CTCF binding sites are highly conserved between tissues and cell lines [46], we used the publically available ChIP-seq datasets of the ENCODE consortium [42] and displayed CTCF binding sites from K562 human monocytic leukemia cells, HUVEC human endothelial cells and NHEK human epidermal keratinocytes over the whole CXCL cluster and its upstream and downstream flanking genes (Figure 1A). This evidence concerns the gene CTCF and monocytic leukemia.